A friend of mine did it, at 30. It sounded like a good plan. Living in a developing country with a small capital. Ten years later, he's broke, isolated, unable to travel or to access good medical care or even to provide good education to his daughter. At 40, after 10 years of doing nothing in a poor country, he has very limited options to make money.
Another thing to keep in mind is that retiring implies a change in lifestyle. Once you get used to a lifestyle, it's difficult to go back.
To answer the question, I think I'll retire the day where I'm unable to work. Hopefully not before my 60s.